Recently thin films of amorphous chalcogenide glasses have been investigated as inorganic resists for microlithography. These materials offer an attractive potential alternative to polymer resists because of a number of advantages, such as the possibility of preparing physically uniform films of thickness as small as 200 A with insignificant numbers of pin-holes, mechanical, optical and thermal stability, compatibility with dry processing, and the possibility of obtaining both positive and negative resist action in the same material under different processing conditions. In addition, these films are resistant to strong acids such as HCl, H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, and HF. Patterns can directly be etched on Si, Si.sub.3 N.sub.4, and SiO.sub.2. However, the sensitivity of the positive resist is rather poor. Moreover, the difference in solubility between exposed and unexposed portions of the as-deposited films is not much, resulting in poor contrast. Since an amorphous film is in a metastable state, its structure can be changed by suitable radiation. Some of the physical and chemical properties are affected by the structural changes providing, therefore, the possibility of enhancing the radiation induced effects pertinent to lithographic behavior of these films.
Pattern generation in inorganic resists has been demonstrated by optical [Nagai et al., Appl. Phys. Lett., 28 145 (1976); Yoshikawa et al., Appl. Phys. Lett., 29 677 (1976); Tai et al., 155th Electrochem. Soc. Spring Mtg. May 1979; Tai et al., J. Vac. Sci. Technol., 16 1977 (1979); Balasubramanyam et al., Bull. Am. Phys. Soc., 25 3 (1980); Chang et al., Appl. Phys. Lett., 33 892 (1978); Chang et al., Opt. Commun., 24 220 (1978)], electron beam [Yoshikawa, Appl. Phys. Lett., 31 161 (1977)] and X-ray [Kolwicz et al., J. Electrochem. Soc., Solid St. Sci. and Technol., 127, 135 (1980)] lithographic techniques.